The gift acknowledges the help Halifax received from Boston 100 years ago after the Halifax Explosion

The 16-metre white spruce is destined for Boston. (Michael MacDonald/The Canadian Press )

Robert Young and his six-year-old son Jack made a special trip to city hall in Halifax on Friday to bid farewell to a big tree.

They were among about 300 people who gathered at the city's blustery Grand Parade square for an annual tradition: the official send-off for a huge Christmas tree destined for Boston — a gift meant to show Haligonians' gratitude for the help Bostonians provided after Halifax was devastated by an explosion 100 years ago.

"When we heard about the tree coming to the parade square, Jack hopped on his scooter and we got over here and made it in time for the big show," said Young, who conducts historic walking tours of Halifax.

"It's an important gift because of Boston's role in responding so quickly to the crisis. [Halifax] had run out of medical supplies. There was a shortage of nurses and doctors. Right away, Boston sent an emergency train through a blizzard to Halifax and contributed all sorts of money and help. It's vital to appreciate that."

Tree from Cape Breton

Caused by the collision of two wartime ships — one of which was carrying explosives — the Halifax Explosion killed about 2,000 people, wounded 9,000 and flattened a wide swath of the port city, including a Mi'kmaq village on the other side of the harbour.

The blast on Dec. 6, 1917, remains one of Canada's worst human-caused disasters.

The tree from Cape Breton made a stop in Halifax before its 1,100-kilometre journey to Boston. (Brett Ruskin/CBC)

Young said his son became intrigued with the story behind the tree after the two read a fictional children's book that featured two squirrels travelling to Boston on the tree.

When asked what he thought about what the people of Boston did to help Halifax, the wide-eyed little boy uttered one word: "Helpful."

On the street beside city hall, a gleaming yellow truck arrived carrying the 16-metre white spruce on a flatbed trailer with a police motorcycle escort leading the way. The 45-year-old tree, with a Nova Scotia flag fastened to its side, was cut down in a ceremony Wednesday in Blues Mills, about 38 kilometres from Baddeck in Cape Breton.

More than a decoration

Among the dignitaries on hand for Friday's ceremony was Kelly Craft, the new United States ambassador to Canada.

"We are always there for each other in times of tragedy," Craft told the crowd, noting that Haligonians and Canadians in general helped their American neighbours after the 9/11 terrorist attacks in 2001 and the bombing of the Boston Marathon in 2013.

Halifax Mayor Mike Savage said the tree was much more than a holiday decoration.

"It's an enduring symbol of our deep appreciation for the tremendous assistance we received from the state of Massachusetts following the explosion 100 years ago," he said.

Tree lighting taking place Nov. 30

Jamie Rouse and his wife travelled from nearby Cow Bay, N.S., to be part of the ceremony, which included scores of rosy-cheeked schoolchildren sipping free cider and eating hot dogs and Nova Scotia apples.

"It's about unity," he said, a tuque pulled down over his ears to fend off the cold gusts of wind that swept across the square. "It brings everyone together."